Packing for centrifugal pumps



p 29, 1931- c. A. SCHELLENS 1,825,251

PACKING FOR CENTRIFUGAL PUMPS Original Filed Jan. 12. 1927 2 SheetsSheet 1 INVENTOR WYM ATTORNEY! p 29,'1931- c. A. SCHELLENS 1,825,251 v PACKING FOR QENTRIFUGAL PUMPS Original Filed Jan. '12. 1927 2 Sheets-Sheet 2 INVENTOR flwq m 4M mmpww ATTORNEY$ ing means in association therewit and Patented Sept. 29, 1931 umrao STATES cmus'rornxa a. scnmmts, or

ENGINEERING COIPANY, OI-ENGLEWOOD, m JERSEY, A OOBIOELTIOI 01' m.

WARE

Serial as. 728,409. fled July 1, 1024; am: Io. $51301.

This invention relates to improvements in centrifugal pumps and is particularly useful as a boiler feed water pump.

This application is a division of my conding application, Serial No. 160 539, filed anuary 12, 1927, which, in turn, is a division of my application Serial No. 723,469, filed July 1, 1924, now issuedas Patent No. 1,664,488 of April 3, 1928.

Centrifugal pumps for feeding boilers, such as locomotive boilers for example, must be well adapted to deliver at small volumes and high pressures, and I, therefore, provide a high speed centrifugal pump having such characteristics.

In pumps of this character difliculties are encountered from leakage, particularly since it is necessary to maintain a sensible clearance between the pump runner and the pump casing. In this connection it is pointed out that the water, in passin through the runner, develops considera 1e pressure, and leaks back, and where the delivery volume is small, this leakage, which is a dead 1058, forms a large proportion of the delivery volume, and is, therefore, prohibitive.

The primary ob'ect of my invention is to overcome these di culties.

More specifically stated, it is an object of my invention to provide very effective sealing means in pumps of the character described whereby hig pressure leakage is prevented.

How the foregoing, together with such other objects and advantages as may hereinafter appear, or are incident to m invention,

are realized is illustrated in pre erred form in the acoompanying'drawin wherein- Fig. 1 is a section throu a pump constructed in accordance wit my invention with certain of the parts appearing in elevation.

Fig. 2 is an enlarged view showing the runner partly in elevation and partly in section, and illustrating my n im roved seal- 3 is a face view of a sealing ring. In the drawings, thepump A, in general, comprises a casing 4 having a water inlet 5 to the pump bowl 6, around which there is the PATENT OFFICE IASSAOEUSIPI'S, M6103 IO PACKING: I03 WUGAII Original application Medium 18, 1987, Serial Io. 160,589 which in turn is a division of application divided and this application lied larch 90, nae. Ierial disch'ar e chamber 7 having an outlet 8 to the boi er; and a runner or impeller C secured to the end of the drive shaft 9 the shaft being threaded into the face of the runner casting opposite the intake side and the runner having a hub 10 for this purpose.

- The shaft 9 is supported by suitable bearing The runner C has an axial intake and a radial discharge from its periphery. It has a plurality of water passages a terminating at the entrance or intake side in a plane perpendicular to the axis of rotation, the intake ends of said passages being arranged in a circular group on a small radius around the central boss or crown 12. The walls between the passages constitute cutting blades. The runner illustrated is of the form shown in my Patent No. 1,664,488 issued April 3, 1928.

By employing such a runner havin an inlet eye of small diameter, I am enabl to employ a correspondingly small diametered inlet throat or nozzle, and thus I am enabled to cut down the amount of leakage very materially.

In the drawings the nozzle or throat is indicated at 16, and it is in a sense a floating member arranged to prevent leakage because of the following provision.

The throat 16, in this instance, comprises a ring 17 having inner flanges 18 and 19 extending from opposite faces thereof. The flange 18 slidably fits in the sleeve 20 threaded into the bowl of the pump, and the ring can thus shift axially. The ring is prevented from rotating by means of the pin 21.

The body of the ring lies in the "pressure space of the bowl, and since the external diameter of the flange 19 is less than the exter nal diameter of the flange 18, the area of the face of the body of the ring toward the impeller is greater than the area of its other face. The outer flange 22 of the ring has less depth than the flange l9.

Stated more specifically, and referring to Fig. 2, the external diameter 19a of the flange 19 is less than the external diameter 18a of the flange 18, and, therefore, the area a of the face of the body of the ring toward the impeller is greater than the area b of its other ace.

The operation is as follows. Assuming that the pump is at rest and the flange 19 is in contact with the runner, on starting up, the ring will be subject to unbalanced pressure which will move the ring away from the runner axially. As the ring moves a gap is opened between the flange 19 and the runner, and the ratio of clearance, as between the flange 19 and the runner to that between the flange 22 and the runner, will increase, in consequence of which the pressure between the ring and the runner decreases. (The same result could be obtained by drillin holes in the flange 22, instead of making it of less depth.) Soon a point is reached where the force tending to push the ring away from the runner is balancedby the pressure on the back of the ring-and the-ring stays put at a definite clearance from the runner. By proper proportioning, this clearance can be accurately determined'in advance, and I prefer to so proportion the parts as to maintain a clearance of from .001 to .002 of an inch. With this clearance, the leakage is not sufficient to impair the efliciency of the pump in an amount which would render the pump unsuitable for the use intended, while, at the same time, rapid wear is avoided, and the pump will remain in satisfactory operating condition for long periods. While I prefer to proportion flanges 18 and 19 so as to obtain a slight clearance between the ring 17 and the runner C as described above, I may so proportion these flanges as to permit the ring to touch the impeller with alight pressure between the surfaces in contact.

In further explanation of: the above, let us assume that the ring 17 is touching the impeller, as shown in the drawings, and that there is clearance at 22a, under which conditions full discharge pressure will build up in the chamber D. However, since the inner flange 19 has less diameter than the flange 18, the ring will be subject to a pressure differential and move away from the impeller, immediately opening clearance between flange 19 and the impeller. This immediately reduces the pressure in chamber D, but this pressure adjusts itself so as to produce a very small clearance between the sealing ring and the impeller.

It will be noted that the inner diameter of the throat 16 corresponds to the outer diameter of the inlet eye of the impeller, and that, as the inlet eye is of small diameter, the diameter of the sealing flange 19 is also small,

vsuch clearance at a minimum so that the loss through leakage is kept within allowable limits.

Referring to Fig. 3, it will be seen that the face of the ring which faces the impeller has an interrupted groove 24 leaving several ribs 25 having the same depth as the flange 19 which tend to prevent cocking of the ring.

I claim 1. In a centrifugal pump, the combination of a casing, a runner, and a packing member having a leak restraining connection with one of said elements permitting of axial motion relative thereto, said member having means whereby it is held removed by a small clearance from the other element under influence of fluid pressure.

2. In a centrifugal pump, the combination of a casing, a runner, and a packing member having a leak restraining connection with one of said elements permitting of axial motion relative thereto, said member having a face adapted for possible contact with an adjacent face of the other element, and means effecting a pressure holding of said faces apart by a slight clearance.

3. In a centrifugal pump, the combination of a casing, an impeller, and a packing device for preventing high pressure leakage to the inlet side of the pump, said device comprising a floating member having a portion adapted to be pressure held removed from the impeller by a small clearance and a portion effecting such operation of the member. I 4. In acentrifugal pump, the combination with its impeller and casing, of a floating packing member guided in the casing and operatmg to maintain a seal against high pressure leakage past the impeller to the suction side of the pump, said member having an inner annular rib, an outer annular rib of less depth than the inner rib and a connecting web forming a chamber having communication with high pressure fluid, the face of said inner rib being adapted to coact with a face of the impeller to form the aforesaid seal, and the face of the outer rib being arranged to be in spaced relation to a face of the impeller to form a fluid inlet to the aforesaid chamber.

In testimony whereof I have hereunto signed my name.

CHRISTOPHER A. SCHELLENS. 

